The ornamental design for a plasticcontainer, as shown and described.
FIG. 1 is a top, front, left side perspective view of a plastic container showing my new design;
FIG. 2 is a front elevational view of FIG. 1;
FIG. 3 is a rear elevational view of FIG. 1;
FIG. 4 is a right side elevational view of FIG. 1;
FIG. 5 is a left side elevational view of FIG. 1;
FIG. 6 is a top plan view of FIG. 1; and,
FIG. 7 is a bottom plan view of FIG. 1.
The evenly-dashed broken lines in the drawings illustrate the portions of the design that form no part of the claim. The dot-dot-dash broken lines in the drawings define the bounds of the claim and form no part thereof.